Thread inspection is a necessary part of many manufacturing or quality control procedures. It involves the spinning of externally or internally threaded gauges into threaded holes or onto threaded studs respectively. These threaded holes or studs may be integral parts of machines or perhaps just fastener parts such as nuts or bolts. Power driven spindles on which gauges are fitted to facilitate rapid and uniform testing are used.
The prior art includes U.S. Pat. No. 4,926,700 of Peplinski for a blind hole thread gauge using a modified commercial nut driver. This bench mounted device uses strain gauges to monitor torque during testing, as well as sensing when a given hole has been tested to its proper depth. U.S. Pat. No. 7,059,055 of Wickham et al. is a commercial tester for checking thread presence in blind holes rapidly. Both single spindle and multi-spindle devices are described using adjustable slip clutches to limit the torque applied during testing. Upon detecting the proper depth of testing or upon exceeding the torque limit, the tester automatically reverses the drive motor to disengage the gauge from the hole being tested.
Additionally, Peplinski '700 uses an electrical contact at the distal end, which closes a circuit when it touches the machine part. This electrical contact is rotated with the gauge, causing possible abrasion at the point of moving contact.
The prior art does not reveal a compact hand-held ergonomic thread inspection tool that is power driven, and uses a mechanical clutch as a surrogate for torque to initiate either automatic withdrawal or alert the user to operate the reversing switch manually in case of jamming.
The prior art also shows the compact hand-held manual adjustable torque thread gauge of Kolkind (U.S. Pat. No. 7,484,427). This interposes an adjustable magnetic torque limiting clutch between the handle, which is manually rotated, and the thread gauge at its front end.